PS3-23. Effects of Saponins and Phenolic Compounds in Fenugreek on Ruminal Fermentation and Methane Production In Vitro.

Abstract Naturally occurring plant compounds have the potential to modulate nutrient metabolism, improve animal health and enhance productive performance if they possess positive biological activities. Fenugreek (Trigonella foenum-graecum L; FG), an annual legume forage, contains an array of plant bioactives including saponins, phenolics and phytosterols. However, information regarding their effects on nutrient digestion and metabolism are lacking. The objective of this study was to assess the effects of saponins and phenolics in FG on rumen fermentation and methane (CH4) production. Crude extracts of saponins and phenolics were prepared from whole-plant FG harvested 9 wk post sowing. In vitro ruminal incubations were conducted over 48 h in 125-serum vial with alfalfa hay as the substrate and rumen fluid collected from cattle fed alfalfa hay used as the inoculum. Treatments included FG saponins at 45, 90 and 180 µg/ml, phenolics at 80 µg/ml and mixture of saponins (90 µg/ml) and phenolics (80 µg/ml). The experiment was repeated thrice. Saponins at 45 to 180 µg/ml linearly decreased dry matter disappearance (DMD; p = 0.027) and NH3 concentration (p < 0.001), increased total volatile fatty acids (TVFA; p = 0.002) at 24 h, but had no effects on them after 48 h. Microbial protein synthesis (MPS) was linearly increased (p = 0.005) by saponins at 48 h but not at 24 h of incubation. Phenolics at 80 µg/ml decreased (p = 0.006) MPS at 24 h but increased (p = 0.002) it after 48 h of incubation. Total gas production was not affected by saponins but was increased by phenolics (p < 0.001) during the 48- h incubation. CH4 production (ml/g DM) was linearly decreased by saponins (p = 0.032∼< 0.001) and phenolics (p = 0.007∼< 0.001) over 24 h of incubation. Combining saponins and phenolics additively reduced (p = 0.01) CH4 production. Saponins and phenolics alone and in combination reduced (p < 0.001) acetate:propionate ratio at 24 and 48-h incubation via increasing molar proportion of propionate. Saponins and phenolics in FG possess biological actives that favorably modulate rumen fermentation and could enhance the inherent feed value of FG as alternative legume forage.